This invention relates to a variable capacity vane compressor which is intended to improve the protection of a seal member, etc. employed therein.
Conventionally, variable capacity vane compressor has been proposed e.g. by Japanese Provisional Patent Publication (Kokai) No. 64-36997, which is adapted to compress a refrigerant gas circulating in an air conditioning system for automotive vehicles.
The proposed compressor comprises a cylinder having a pair of side blocks closing opposite ends thereof, a rotor rotatably received within the cylinder, a discharge pressure chamber arranged at one side of the cylinder close to one of the side blocks, a first oil sump formed in a bottom of the discharge pressure chamber, a suction chamber arranged at the other side of the cylinder close to the other side block, a second oil sump formed in a bottom of the suction chamber, an oil passageway communicating between the first and second oil sumps, a control element arranged in the other side block for rotation about its own axis in opposite directions to thereby vary the compression starting timing, and a seal member fitted on the control element.
As shown in FIG. 1, the control element 150 has one end face thereof formed integrally with a pair of pressure-receiving protuberances 150a projected therefrom (only one of which is shown). The other side block 160 has an end face facing the rotor 170 in which an annular recess 160a is formed. The control element 150 is rotatably fitted in the annular recess 160a such that the pressure receiving protuberances 150a are slidably received in respective pressure working chambers defined in a bottom of the annular recess 160a to divide each pressure working chamber into a high pressure chamber 123.sub.2 and a low pressure chamber, not shown.
With such an arrangement, the control element 150 rotates in response to the difference in pressure between the low pressure chamber and the high pressure chamber 123.sub.2, to vary the compression starting timing and hence the capacity of the compressor. To ensure smooth rotation of the control element, the seal member 164 is fitted along an outer peripheral edge of each pressure receiving protuberance 150a, which is kept in gastight slidable contact with inner surfaces of the pressure working chamber, with a constant clearance provided between the pressure receiving protuberance and the pressure working chamber to heremetically seal the same chamber while allowing the pressure receiving protuberance 150a to slide on the chamber walls.
According to the proposed compressor, a short passageway, which is formed by a passage 200, a pressure chamber 201, and a passage 202, extends between a discharge valve chamber 142 and the high pressure chamber 123.sub.2, to introduce compressed discharge gas from the discharge valve chamber 142 into the high pressure chamber 123.sub.2, thereby creating a control pressure within the high pressure chamber 123.sub.2, as shown in FIG. 1.
However, the temperature of the compressed discharge gas delivered into the high pressure chamber 123.sub.2 is rather high, particularly when the compressor is in partial capacity operation. As a result, the seal member 164 is heated by the compressed discharge gas to become deteriorated, resulting in a shortened life of the seal member 164. In the worst case, the seal member 164 is broken upon rotation of the control element 150, whereby the gastightness by the seal member 164 is lost to make it impossible to carry out accurate capacity control. Besides, the broken seal member 164 can be caught in the annular recess 160a to impede rotation of the control element 150.